1. Field of the Invention
This invention relates to the field of data storage and, more particularly, to the mirroring of data.
2. Description of the Related Art
As computers and data processing services become more important to modern business, ensuring the reliability and availability of each individual component resource also becomes increasingly important. Specifically, the storage systems used to store and access data must be faster, cheaper, more fault-tolerant and accessible at all possible times.
One solution is to provide a volume manager operable to manage a plurality of data storage devices for a top-level file system. All the complexity of managing data across multiple devices may be handled by the volume manager, thereby providing the top-level file system with the illusion of a single, high-availability storage device.
For example, a volume manager may manage a mirrored pair of disk drives, wherein the same data is written to both disks. A mirrored pair of disk drives may provide for increased reliability, since in the event of a single disk drive failure, the mirrored disk drive is still operable to provide access to the data. Mirrored disk drives may also provide for increased data throughput, since each disk is capable of simultaneously executing a read or write access. Furthermore, the mirrored disk drives may be network devices located in different areas, thereby providing increased security against damage or theft at a single location.
However, a typical volume manager manages data at the volume level, rather than at a finer level of granularity. Accordingly, when a particular volume is mirrored, the data blocks corresponding to all files stored in that volume are mirrored, regardless of the importance (or desired storage quality) of each individual data file.